The Trenton Group (Upper Ordovician Series) of Eastern North America

1988 ◽  
Author(s):  
Brain D. Keith
Keyword(s):  
North America ◽  
Eastern North America ◽  
Upper Ordovician ◽  
Trenton Group

Designation of a neotype and paraneotype for Conularina triangulata (Raymond, 1905) (Upper Ordovician, eastern North America)

2020 ◽  
Vol 94 (4) ◽  
pp. 796-797
Author(s):  
Heyo Van Iten ◽  
Mario E. Cournoyer ◽  
Michelle Coyne
Keyword(s):  
New York ◽  
North America ◽  
Late Ordovician ◽  
Quebec City ◽  
Eastern North America ◽  
Upper Ordovician ◽  
Thrust Sheet ◽  
City Formation ◽  
Early Late

Conularina triangulata (Raymond, 1905), the genotype of Conularina Sinclair, 1942, is a rare, early Late Ordovician conulariid (Cnidaria, Scyphozoa; Van Iten et al., 2006) having three sides or faces instead of four (Sinclair, 1942, fig. 9; Van Iten, 1992, text-fig. 3E). Originally described from the Valcour Formation (early Sandbian; Dix et al., 2013) on Valcour Island, New York (Sinclair, 1942), C. triangulata has since been found in laterally equivalent strata of the upper Laval Formation (‘Upper Chazy’; Sinclair, 1942) in Laval, Québec, Canada (Sinclair, 1942). From this same unit and area, Sinclair (1942) erected three new, four-sided species of Conularina (C. irrasa, C. raymondi, and C. undosa), and he erected a single four-sided species (C. narrawayi) from the Ottawa Formation (now the Sandbian–Katian Ottawa Group; Dix et al., 2013) at Tétreauville (now Gatineau), Québec. Subsequently, Jerre (1994) reported the occurrence of two species of Conularina in the Upper Ordovician of Sweden. Jerre (1994) also proposed that Eoconularia? forensis Sinclair, 1946 from the Upper Ordovician Citadelle Formation (‘Quebec City’ Formation; Sinclair, 1946) in Québec City, Québec (Promontoire de Québec thrust sheet, Appalachian Humber Zone, Allochtonous Domain; Castonguay et al., 2002) is a species of Conularina.

scholarly journals Taxonomy and evolution of the Orthograptus quadrimucronatus species group (Graptolithina)

1992 ◽  
Vol 6 ◽  
pp. 110-110
Author(s):  
Daniel Goldman
Keyword(s):  
Great Britain ◽  
North America ◽  
Species Group ◽  
Eastern North America ◽  
Upper Ordovician ◽  
Size Change ◽  
Utica Shale ◽  
Morphological Differences ◽  
Changes Over Time ◽  
Northern Appalachian Basin

The Middle to Upper Ordovician graptolite taxon Orthograptus quadrimucronatus currently comprises 11 sub-species and has several closely related species. Many of these subspecies are poorly defined, having been established on the basis of stratigraphic and geographic occurrence and not morphological differences. A detailed morphometric analysis of this group indicates that all 11 subspecies of O. quadrimucronatus and the morphologically similar British species, O. pageanus, can be placed within three distinct lineages. Members of the O. pageanus lineage are characterized by long apertural spines on the first two thecae, a broad proximal end, and a wide less densely thecate rhabdosome. Specimens belonging to the O. quadrimucronatus spinigerus lineage have narrow proximal ends, rapidly widening rhabdosomes, and elongated apertural spines on the 8th to 12th thecal pairs. The O. quadrimucronatus quadrimucronatus lineage is composed of specimens with no unusual spines and rather parallel sided rhabdosomes.Orthograptus pageanus first appears in the lower Corynoides americanus Zone and is probably derived from the O. calcaratus species group. O. pageanus retains the large basal spines, robust rhabdosomes, and long thick nema found in O. calcaratus. The thecae of O. pageanus are, however, highly derived with respect to O. calcaratus whose thecae retain the form of their hustedograptid ancestry. O. pageanus has everted thecal apertures and paired apertural spines as opposed to the introverted thecal apertures and apertural horns present in O. calcaratus. O. quadrimucronatus quadrimucronatus appears at approximately the same time as O. pageanus while O. q. spinigerus appears slightly later in Australia and Great Britain and several graptolite zones later in eastern North America. The first appearance of all three lineages in the classic graptolite-bearing rocks (Utica Shale) of the northern Appalachian basin represents immigration and not speciation. Members of the O. pageanus lineage grow rapidly in size through the C. americanus Zone and become extinct at or just above the top of the zone. The O. q. quadrimucronatus lineage shows no single trend through time, getting larger and smaller, seemingly in response to changing water chemistry and temperature. Poor preservation of collections of O. q. spinigerus make within lineage changes over time impossible to evaluate.Specimens of these three lineages were examined across an interval of time representing four graptolite zones (C. americanus to G. pygmaeus zones) in the Middle and Upper Ordovician rocks of Australia, Great Britain and eastern North America. This interval is generally regarded as having a duration of approximately four million years. Across this interval each of these lineages appears to be a stable entity in space and time. Although there are changes in size among members of a lineage during its existence, there are no basic changes in form. Thus, the anagenetic change in these organisms does not appear to produce any new species or even sub-species. New taxa appear with no evidence of ancestral intermediates, and remain basically the same throughout their duration. This pattern is consistent with punctuated equilibrium, although anagenetic size change is also observed.

Mohawkian (Upper Ordovician) conodonts of eastern North America and Baltoscandia

2000 ◽  
Vol 74 (6) ◽  
pp. 1122-1147 ◽  
Author(s):  
Stephen A. Leslie
Keyword(s):  
New Species ◽  
North America ◽  
Eastern North America ◽  
Zone Boundary ◽  
Upper Ordovician

A collection of 57,877 conodont elements that includes 39 species representing 30 genera was made from the upper part of the Phragmodus undatus Zone and the lower part of the Plectodina tenuis Zone (late Turinian–early Chatfieldian). Conodont samples were collected from 30 sections in eastern North America and Baltoscandia, where the P. undatus–P. tenuis Zone boundary projects into B. alobatus Subzone based on K-bentonite bed correlation. Elements previously assigned to form-species of Oistodus are shown to be apparatus associates in coniform apparatuses of Besselodus. Pseudobelodina manitoulinensis new species is described and the apparatus-based taxonomy of Scyphiodus primus and Staufferella polonica are proposed.

Petrology and potential tectonic significance of a K-bentonite in a Taconian shale basin (eastern Ontario, Canada), northern Appalachians

2005 ◽  
Vol 142 (2) ◽  
pp. 145-158 ◽  
Author(s):  
SAJAL SHARMA ◽  
GEORGE R. DIX ◽  
MIKE VILLENEUVE
Keyword(s):  
North America ◽  
Compositional Data ◽  
New York State ◽  
Age Dating ◽  
Distribution Area ◽  
Eastern North America ◽  
Upper Ordovician ◽  
Volcanic Source ◽  
External Process ◽  
Eastern Ontario

A 6 cm thick K-bentonite, herein defined as the Russell Bed, occurs in an Upper Ordovician deep-basin shale succession in eastern Ontario, Canada, forming part of the distal Taconic foreland in eastern North America. The bed lies within the pygmaeus graptolite Biozone, which is about 451 to 452 Ma in age. Although some bentonites are reported from this interval in eastern North America, we are reporting the first set of compositional data for a bentonite of this age. Gamma-log correlation identifies a potential minimum distribution area of <2×105 km2 for the K-bentonite, covering part of southern Quebec, New York State and eastern Ontario. The deposit coincides with the first influx of distal turbdites into this shale basin, associated with Taconic flysch, and simultaneous abrupt ventilation of the once anoxic deep-water basin, which had formed initially after foundering of the Upper Ordovician carbonate platform. Concurrent intrabasinal extinction of several graptolite species suggests that change in sedimentation, palaeoceanography and volcanism were linked to a regional external process. Compositionally, the bentonite is distinct from the older Ordovician platform deposits in eastern North America. The deposit contains abundant titaniferous phlogopite with 1.6% BaO, fluoroapatite with 2.5% F, and dynamically shaped glass spherules now altered to clay. The spherules and clay matrix constitute 45% of the bed and, compositionally, define an illite (>90%)–smectite (I/S) structure with about 7.5% K2O%. Age-dating by Ar–Ar analysis of the phlogopite crystals yielded a younger than expected (440–445 Ma) age. This difference, along with evidence of localized chloritization of phlogopite, likely reflects known post-Ordovician hydrothermal activity within the basin. On the basis of several geochemical proxies, the magmatic source of the Russell K-bentonite falls within the trachyandesite field and was Ba-enriched. Comparison of geochemistry and mineralogy with older, Middle to Late Ordovician and younger Early Silurian K-bentonites within the Taconic orogen along eastern Laurentia and Baltica reveals that the potential source magma for the Russell Bed was more mafic, more alkaline, and less fractionated than sources typical of older (platform) bentonites. Instead, it is more similar to the younger Llandovery bentonites of Scandinavia and Scotland. It remains uncertain if it signals local or regional compositional change in volcanic source in the northern Appalachians.

Late Ordovician - Early Silurian cryptospore occurrences on Anticosti Island (Île d'Anticosti), Quebec, Canada

2007 ◽  
Vol 44 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Jeffery G Richardson ◽  
William I Ausich
Keyword(s):  
North America ◽  
Late Ordovician ◽  
Land Plants ◽  
Eastern North America ◽  
Upper Ordovician ◽  
Lower Silurian ◽  
Low Diversity ◽  
Anticosti Island ◽  
Early Land

Residues from Hirnantian (Upper Ordovician) and Aeronian (Lower Silurian) strata of Anticosti Island, Quebec, Canada, have yielded the oldest occurrence of terrestrial-based palynomorphs (cryptospores) from eastern North America. A low-abundance, low-diversity cryptospore assemblage containing specimens of Pseudodyadospora, Velatitetras, and alete monads has been recovered from the Velleda Member of the Ellis Bay Formation (Upper Ordovician, Hirnantian). The Gun River Formation (Lower Silurian, Aeronian) contains a low-abundance, low-diversity assemblage composed of specimens of Velatitetras, Laevolcancis, and alete monads. The occurrence of these assemblages provides evidence for early land plants in this part of North America during the Late Ordovician and Early Silurian, and documents the existence of a terrestrial-based flora during and after the Saharan (Late Ordovician) glaciation.

Review of some species of Favistina, Nyctopora, and Calapoecia (Ordovician corals from North America)

1976 ◽  
Vol 113 (5) ◽  
pp. 457-467 ◽  
Author(s):  
R. K. Jull
Keyword(s):  
North America ◽  
Eastern North America ◽  
Upper Ordovician ◽  
Thin Sections ◽  
Middle Ordovician

SummaryMaterial from the H. A. Nicholson collection, University of Aberdeen, provides information on three of Nicholson's species. Syntypes of Favistina calicina are described and the lectotype designated. Topotypes of Nyctopora billingsii are compared with an earlier description of the type thin sections. Columnopora cribriformis is considered synonymous with Calapoecia huronensis Billings, itself a poorly understood species; redescription of the type of the latter species shows it to be separate from C. canadensis Billings. Calapoecia ungava Cox is reinterpreted with a lectotype designated, and Nicholson material is placed with this species. All specimens are from eastern North America and of Upper Ordovician age excluding the Middle Ordovician N. billingsii and C. canadensis.

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